Exhaust system

ABSTRACT

An exhaust system for internal combustion engines, including the Wankel engine, comprises a plurality of very thin silencing members arranged in series and of the straight through flow type, the silencers preferably including an outer tube of an oval shape that longitudinally contacts both sides of an inner gas flow tube that is suitably perforated to cooperate with silencing means in the space between the outer shell and the flow tube.

United States Patent [1 Heath et a1.

[451 Feb.26, 1974 EXHAUST SYSTEM Robert A. Heath, Racine, Wis.; Ronald J. Martoia, Jackson, Mich.

Assignee: Tenneco Inc., Racine,.Wis.

Filed: Mar. 9, 1972 Appl. No.: 233,211

Related US. Application Data Continuation-in-part of Ser. No. 868,283, Oct. 13,- 1969, Pat. No. 3,648,803, which is a continuation of Ser. No. 531,245, March 2, 1966, abandoned.

Inventors:

u.s. C1. 181/48 Int. Cl. F01n 1/00 Field of Search... l8l/48, 47 R, 47 A, 47 B, 59

References Cited A UNITED STATES PATENTS Wilson 181/48 3,196,976 7/1965 Powers et a1. 181/48 3,289,785 12/1966 Walker 181/48 3,338,331 8/1967 Jettin'ghoff 181/48 3,402,785 9/1968 Powers et al. 181/48 Primary ExaminerStephen J. Tomsky Attorney, Agent, or Firm-Harness, Dickey & Pierce [5 7] ABSTRACT An exhaust system for internal combustion engines, including the Wankel engine, comprises a plurality of very thin silencing members arranged in series and of the straight through flow type, the silencers preferably including an outer tube of an oval shape that longitudinally contacts both sides of an inner gas flow tube that is suitably perforated to cooperate with silencing means in the space between the outer shell and the flow tube.

3 Claims, 11 Drawing Figures PATENTE FEB 2 6 I974 SHEET 1 0F 2 .llIlIl-lll 1 EXHAUST SYSTEM RELATED APPLICATION This application is a continuation in part of our copending application U. S. Ser. No. 868,283 filed Oct. 13, 1969 (now U. S. Pat. No. 3,648,803); which in turn, was a continuation of U. S. Ser. No. 531,245 filed Mar. 2, 1966 and later abandoned.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention to provide an exhaust silencing system that is suitable for use with Wankel engines and other internal combustion engines. It is also an object of the invention to provide a highly effective exhaust silencing system that is compact, of minimum height, includes a relatively small number of components, is relatively easy to produce, and which is capable of attenuating a wide range of sound frequencies.

While the exhaust system of the present invention is very suitable for conventional piston-type internal combustion engines, it will be of particular advantage in vehicles having a Wankel engine since these, in all probability, will be of smaller size and in need of the minimum space requirements associated with systems of the present invention. Furthermore, the Wankel engine emits a higher frequency range than a conventional piston engine and the flattened outer shells used in the presentsystem are especially sensitive to high frequency tuning, thereby providing a definite advantage in attenuating this type of engine.

In accordance with the invention, an exhaust system includes a plurality of silencers which have outer shells that are extremely small in at least one direction, preferably the vertical dimension. They preferably have straight through gas flow tubes that are suitably perforated to open into chambers in the outer shell which are, in part, defined by the flow tubes. Chambers are transversely formed within the shells by partition means in the form of portions of opposite faces, preferably the top and bottom sides, of the shell which engage each other so that a series of different length chambers result to give means for silencing a range of troublesome frequencies.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view, partly in section, of an exhaust system embodying the invention for use with a Wankel engine;

FIG. 2 is an enlarged cross section through one of the silencers in the system of FIG. 1 as taken along theline 2-2 of FIG. 1;

FIG. 3 is an enlarged perspective view of a silencer of the type used as the first element in the system of FIG. 1 and shown in FIG. 2;

FIG. 4 is an enlarged longitudinal cross section through the last silencing element used in the system of FIG. 1;

FIG. 5 is a cross section along the line 5-5 of FIG.

FIG. 6 is a schematic view of a modified form of exhaust system embodying the invention also as used with a Wankel engine;

FIG. 7 is an enlarged longitudinal cross section through the first silencingelement in the system of FIG.

FIG. 8 is a cross section along the line 8-8 of FIG. 7;

FIG. 9 is an enlarged longitudinal section through the second silencer in the system of FIG. 6;

FIG. 10 is a crosssection through around tube that may be used to form the various shells used as the outer housing in the silencers shown in the exhaust systems described herein; and

FIG. 11 is a cross sectional view showing how the round shell of FIG. 10 is deformed into an oval shape as used in the housings for the various silencers.

DETAILED DESCRIPTION OF THE INVENTION While the exhaust systems of the invention may be used to silence internal combustion engines that are used in stationary applications or in very large vehicles where ample space is available, it is contemplated that a major application for the systems of the invention will be in modern automobiles, especially small automobiles, where relatively little space beneath the vehicle frame and chassis can be found in which to place the bulky mufflers or silencers. While only a single line exhaust system is shown in the drawings, it is understood that two such systems may be used in dual fashion if desired.

Referring to the exhaust system 1 of FIG. 1, an internal combustion engine 3, such as a Wankel engine, discharges its exhaust gases into an inlet pipe 5 that delivers the gases to a first silencer 7. The silencer 7 is connected by an intermediate conduit 9 to a second silencer 11 which in turn is connected by a conduit 13, which may have the rear axle kick-up arch 15 in it, to a third silencer 17 that in turn empties into a short tailpipe or outlet section 19 that discharges gases into the atmosphere.

A modified exhaust system 21 shown in FIG. 6 is connected to the exhaust manifold or outlet of an engine 23, which also may be a Wankel engine, by means of its inlet conduit 25 which delivers exhaust gases to a first silencer 27. The silencer 27 discharges into a connecting pipe 29, which has an arch section 30 to provide a kick-up over the rear axle of a vehicle, that connects to a second silencer 31 that discharges into a tailpipe section 33 which in turn empties into the atmosphere.

The silencers 7, 17, 27, and 31 are of similar general construction and preferably have outer shells or housings that are originally in the form of a round tube T such as shown in FIG. 10 which is flattened on both sides into an oval pipe 0 as seen in FIG. 11. The oval section tangentially contacts, and is preferably spotwelded to, opposite diametral sides of a gas flow pipe P extending through the shell.

The silencer 11 is shown as being of a different construction wherein the round outer tube, such as tube T of FIG. 10, forms the outer housing 35 which is reduced in diameter at opposite ends to form inlet and outlet necks 37 and 35 that fit around an inner straight through gas flow tube 41. The gas flow tube 41 is preferably perforated throughout its length by means of louvers to open into a chamber 43 formed between it and the shell 35. The volume of the chamber 43, for a ,typical Wankel application, is preferably selected to atthe top and bottom sides to a gas flow tube 47 that provides a straight through gas passage from one end of the unit to the other. If de-sired, the opposite ends of the tube 47 may be enlarged as indicated at 49 to serve as bushings that fit around and may be clamped to the ends of the pipes and 9. The opposite ends of the housing 45 are pinched together as seen at 51 so that U-shaped end sections 52 with top and bottom layers in tight engagement with each other are formed on opposite sides of a circular section 53 that clamps around the tube 47. At an intermediate point in the length of.

the shell 45 opposite sides of the shell are pinched together as seen at 55 in a manner similar to the sections 51 so that the top and bottom of the shell 45 are brought together in tight engagement in U-sections that at their inner ends expand into a circular section 57 that embraces the tube 47 as seen in FIG. 2. The sections 55 act as partitions to subdivide the interior of the housing 45 into four chambers 59, 61, 63, and 65. The tube 47 is perforated preferably by means of louvers, along opposite sides throughout its length in order to open into each of the chambers. For a typical Wankel engine application, the chambers 59 and 61 are preferably of a volume to attenuate sound having a frequency of about 900 cps, the chambers 63 and 65 are preferably of a volume to attenuate sound of about 800 cps.

The silencer 17 comprises an oval housing 67 containing a louvered straight through gas flow tube 69 which is preferably arranged to fit along one side edge of the oval housing 67 as seen in FlGS. 4 and 5. The opposite ends of the housing 67 are pinched or flattened together at 71 as shown for silencer 7 but contain a circular section at one side instead of in the center. The

circular sections embrace the ends of the flow tube 69 and the flat sections close off the opposite ends of the housing. The ends of the flow tube 69 may be enlarged as seen at 73 to provide bushings that receive the ends ofthe connecting pipe 13 and the short tailpipe section 19.

The space inside of the housing 67 is subdivided into a series of chambers 75, 77, and 79 by a pair of pinch-- down sections 81 and 83, which are substantially the same as the sections 71, as shown in FIG. 1. The tube 69 opens into each chamber by means of the louvers extending along one side throughout its length. For a typical Wankel engine application, the chamber 75is preferably sized to attenuate a frequency of about 300 cps, the chamber 77 to attenuate a frequency of about 600 cps, and the chamber 79 to attenuate a frequency of about 500 cps.

With respect to the exhaust system 21, the silencer 27 has an oval shell 85 that tangentially contacts top and bottom sides of a gas flow tube 87 that provides a straight through gas flow path from one end of the silencer to the other. The opposite ends of the tube 87 fit in inlet and outlet bushings 89 and 91 and these are secured in circular sections similar to those shown at 51 (FIG. 3) as formed by pinching or crushing together the top and bottom ends ofthe housing 85 as indicated at 93. The space inside of the housing 85 on one side of the tube 87 is subdivided into chambers 94, 95, 97, and 99 by pinched together sections 101, 103, and 105 in one side of the housing. The space on the other side of the housing is subdivided into chambers 107, 109, and 111 by pinched together sections 113 and 115, the section 115 being shown in FIG. 8. It will be seen that it fits around the supports an end of a tuning tube 117 that connects the chamber 111 with the chamber 109. The tube 87 has louver patches in its sides that open into the chambers 99 and 111 as well as into the chambers 94, 95, 97, and 107. However, that portion of the tube which forms a side of the chamber 109 is imperforate so that the tuning tube 117 provides the only gas inlet and outlet for the chamber 109. Thus, this chamber together with the tuning tube 117 may be tuned in accordance with he Helmholtz formula to attenuate a desired frequency, this preferably being about 160 cps in a typical Wankel engine application. The interior of the tube 87 is connected to the tuning tube 11.9 by way of the chamber 111. The chamber 94 in the typical Wankel engine application for system 21 is preferably of a volume to attenuate about 600 cps, the chamber about 260 cps, the chamber 97 about 800 cps, and the chamber 99 about 400 cps. The chamber 107 is preferably sized to attenuate about 1000 cps.

The silencer 31 has an oval housing 121 which is in the manner shown at 51 pinched together at opposite ends as indicated at 123 to close off the ends of the housing and tightly grip the inlet and outlet bushings 125 which support the opposite ends of the straight through gas flow tube 127. The housing 121' has a pinched together section 129 that subdivides one side of the space on one side of'tube 127 into a chamber 131 and a longer chamber 133. A pinched together section 135 on the other side of the housing subdivides the space between the housing and the tube 127 into chambers 137 and 139. The tube 127 is louvered on opposite sides to open into the chambers 131 and 137. For the typical Wankel engine application, these are preferably of a volume, respectively, to attenuate sound having a frequency of l 100 cps and 900 cps. The tube 127 has a louver patch 14] that opens into one end of the chamber 133 to form a'quarter wave length tuner, the length of the chamber 133 preferably being such as to enable it to attenuate a frequency of about 300 cps.

Similarly, the tube 127 has a louver patch 143 that opens into an end of the chamber 139, the length of which is preferably selected so that it functions as a quarter wave length or Quincke tuner to attenuate a frequency of about 350 cps.

In the various oval silencers described, the flow tube and the various pinches act as partition means to define silencing chambers inside the housings, thereby reducing the number of parts to a minimum. The oval construction reduces the height of the silencers to a minimum to give a good profile and length and facilitate placement under small automotive vehicles, and permits one side of the muffler to operate from the flow tube independently of the other side for either roughness control or tuning'for specific frequencies. The multi-chamber structures permit a wide variety of design frequencies and design frequency bands and ranges to be attenuated so that the cumulative effect is a wide band control. The relatively flat shape of the silencers is particularly sensitive to high frequency and roughness attenuation as required to an increased degree by the higher frequency range emitted by Wankel engines as compared with common piston engines. There is a wide variety of chamber sizes, locations, and combinations to attenuate the Wankels wide range of unpitched sounds, including the nasty burr or snarl of the Wankel. Also, the characteristic Wankel heavy third harmonic over the fundamental or first may be attenuated by the present system. The Helmholtz silencing principle may be used, as in silencer 27, and the quarter wave length may be applied to either side of the flow tube (silencer 31) and discreet frequency tuning can be attained by reflecting the quarter wave. Different frequencies can be reflected in axial directions. Also, one or the other of patches 141 or 143 (FIG. 9), for example, could be located at an intermediate position in their respective chambers 133 or 139 to form a double tuner in the same chamber. The syste, of course, is applicable to piston engines even though the Wankel application is emphasized herein.

Thus, the structures and systems disclosed herein are flexible in nature but highly effective and useful in the design of minimum cost exhaust systems. Modifications in the specific structures and arrangements may be made without departing from the spirit and scope of the invention.

We claim:

l. A silencing device comprising an outer shell of tubular shape and oval cross section, a straight-through inner gas flow tube extending the length of said outer shell and having an inlet at one end of the shell and an outlet at the other end of the shell, opposite sides of the shell at opposite ends being in engagement to form end closures of said shell around said inlet and said outlet,

said outer shell being in engagement with opposite sides of said inner gas flow tube along the full length of the tube, the space between the tube and one side of the shell comprising a longitudinally extending chamber, said inner gas flow tube having openings therein for communication of gas flowing through it with said chamber to effectuate sound attenuation, partitioning means dividing the chamber into two longitudinally spaced silencing chambers, the openings of the inner flow tube communicating with only one of said silencing chambers, and a tuning tube opening at opposite ends respectively into said two chambers and affixed along one of its sides to said gas flow tube.

2. A device as set forth in claim 1 wherein the partitioning means comprises permanently deformed sections of the outer shell engaging each other, the tuning neck, and the respective sides of the inner tube.

3. A device as set forth in claim 2 wherein said inner tube is spaced from two sides of the outer shell whereby longitudinal chambers are defined on opposite sides of the gas flow tube separated from each other by said gas flow tube, said flow tube communicating with said 

1. A silencing device comprising an outer shell of tubular shape and oval cross section, a straight-through inner gas flow tube extending the length of said outer shell and having an inlet at one end of the shell and an outlet at the other end of the shell, opposite sides of the shell at opposite ends being in engagement to form end closures of said shell around said inlet and said outlet, said outer shell being in engagement with opposite sides of said inner gas flow tube along the full length of the tube, the space between the tube and one sidE of the shell comprising a longitudinally extending chamber, said inner gas flow tube having openings therein for communication of gas flowing through it with said chamber to effectuate sound attenuation, partitioning means dividing the chamber into two longitudinally spaced silencing chambers, the openings of the inner flow tube communicating with only one of said silencing chambers, and a tuning tube opening at opposite ends respectively into said two chambers and affixed along one of its sides to said gas flow tube.
 2. A device as set forth in claim 1 wherein the partitioning means comprises permanently deformed sections of the outer shell engaging each other, the tuning neck, and the respective sides of the inner tube.
 3. A device as set forth in claim 2 wherein said inner tube is spaced from two sides of the outer shell whereby longitudinal chambers are defined on opposite sides of the gas flow tube separated from each other by said gas flow tube, said flow tube communicating with said chambers. 